This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The objective of this research project is to visualize the interactions between Kinesin-13 and tubulin rings. The kinesin family of motor proteins utilize energy derived from ATP-hydrolysis to bind, and do work, on microtubules (Vale and Fletterick, 1997. Annu. Rev. Cell Dev. Biol. 13: 745-777). The dynamic nature of microtubules is important for fundamental cellular processes such as spindle assembly during mitosis, cell migration, and cellular transport;in fact, it is the interactions with microtubule associated proteins (MAPS), motor proteins such as kinesin, and other cellular factors, that regulate the dynamic behavior, and so the function, of microtubules (Walczack, 2000. Curr. Opin. Cell. Biol. 12: 52-56). Kinesins are most known for their ability to walk along a microtubular track while carrying cargo from one point in the cell to another;however the intermediate kinesins, of which Kinesin-13 is a member, have not been shown to engage in such a walking motion. Instead, this family of kinesins utilize chemical energy to depolymerize the ends of microtubules. Previous studies have shown that, in the process of depolymerizing microtubule ends, tubulin rings and spirals are formed (Moores et. al. 2002. Mol. Cell. 9: 903-909;Desai et. al. 1999 Cell. 96: 69-78);importantly, addition of Dolastatin to alpha and beta tubulin results in the spontaneous formation of rings indistinguisable from those formed during the depolymerization process (unpublished results). It is thought that these tubulin rings are representative of tubulin configuration at the ends of microtubules, and that studies of motors bound to such rings will give important insights regarding the molecular mechanism of microtubule depolymerization. In the first phase of this project, we will utilize the motor domain of KinI from Plasmodium falciparum (pKinI) to institute an automated platform for data collection and processing via LEGINON and single particle 2D averaging techniques. Once, an automated platform has been established, we will extend our studies to include full-length human kinesin-13 and various truncated versions of the protein. It is the hope that such studies will contribute to our molecular understanding of microtubule depolymerization.